Re: Why not Sony or Oly?

No, Shorter focal length lenses on a smaller sensor do not give the same control over depth of field that an "equivalent" focal length will give on a larger sensor camera.

For an extensive discussion on the pros and cons of various sensor sizes see this...

http://www.sansmirror.com/articles/pick-a-size.html

I do agree with your comments about portability. I would love everything in a small, pocketable package. However, I can't agree that the image quality achievable from a m4/3 in any way rivals a full frame sensor. I'd love to see a FF sensor in a more compact body - I suppose the Leica M9 is currently the smallest option but, as you say, progress is slow.